Immunological techniques will be used to determine the approximate amount of sequence resemblance between related proteins from species of the oxidase-positive Moraxella and organisms presumed to be closely related to Moraxella. The enzymes lactic dehydrogenase and anthranilate synthetase will be purified from two strains of Moraxella. The former enzyme will also be purified from Neisseria catarrhalis. Antiserum, prepared in rabbits against these pure proteins, will be used for immunodiffusion, quantitative precipitin, and microcomplement fixation tests. Immunodiffusion will be used to screen for immunological relationships among these organisms. Cell extracts will be obtained from many catalogued strains of Moraxella and from morphologically similar and possibly related bacteria for this analysis. Quantitative precipitin and microcomplement fixation tests will be used to refine immunological relationships established on the basis of precipitin patterns observed via immunodiffusion. Based on these results, the potential use of these antisera for routine determinative purposes will be evaluated by testing clinical isolates identified as various species of Moraxella, Neisseria, or the Mima-Herellea group.